Amplifier valve for ultra-short waves



Jan. 30, 1951 R. WARNECKE AMPLIFIER VALVE FOR ULTRA-SHORT WAVES FiledAug. 3, 1946 INYENTOR ROBERT WARNEC/(E MAGNETIC FIELD AGENTS PatentedJan. 30, 1951 AMPLIFIER VALVE FOR ULTRA- SHORT WAVES Robert Warnecke,Paris, France, assignor to Compagnie Generals de Telegraphic Sans Fil, acorporation of France Application August 3, 1946, Serial No. 688,359 InFrance February 14, 1941 Section 1, Public Law 690, August 8, 1946Patent expires February 14, 1961 4 Claims. (e1. 315--6) This inventionrelates generally to amplifier valves for ultra-short waves, and moreparticularly to electronic amplifier valves intended to operate atultra-high frequency (in particular decimetric or centimetricelectromagnetic waves).

The characteristics of the invention refer essentially to the particularmethods of association of an electron discharge system employing thesecondary emission, with a system of cavity resonators.

According to the present invention, one employs as an electron amplifiertwo cavity resonators of revolution about the same axis, which areconnected by a metallic pipe, the form, structure and arrangement ofwhich are such that certain of the constructional elements thereof areat the same time the electrodes of an electron multiplier, which meansthat the resultant apparatus considered as a whole as an amplifier forvery short waves has two identical resonant circuits, the quality factorof which is greatly superior to that of the conventional oscillatingcircuits. The replacement of the latter by cavity resonators gives, infact, a high quality factor which leads to small losses and to a largeshunt impedance, otherwise all things being equal. This enables the bestuse to be effected, with very short waves, of the bunching of theelectrons in the electron multiplier and consequently ensures therealisation of amplifier systems having a greatly improved totalefficiency. Conjointly with the very Slight high frequency losses in thecavity resonator (and in the absence of losses by radiation), theamplifier system is then endowed with good stability of frequency.

There will now be described one method of producing cavity resonatorswhich comply with conditions hereinbefore set forth (the embodimentshereinafter set forth being given by way of example only and beingincluded in the invention like the principle itself of the associationcorresponding to the conditions provided for in the precedingexplanation).

The construction of the above-mentioned identical cavity resonatorsaccording to the invention is such that some parts of each of them,separated from the other ones by insulating air tight joints may bepermanently raised to a direct positive voltage with respect to theother parts without preventing the flow of high frequency currentbetween the positive and the negative ones. To get this result, the formand surface of the insulating joints are such that their capacitance isgreat for the high frequency "underfconsideration. According totheinvention, the bottoms of these cavity resonators are provided withcentrally located cathodes, yielding secondary emission electrons, whichcross permeable electrodes, respectively situated at the 2 ends of theconnecting pipe. These electrodes are made positive with respect to thesaid cathodes by means of the above mentioned joints. The high-frequencyoscillations are maintained in both resonators by an oscillator suitablycoupled to them.

Before examining any specific embodiments; corresponding to thepreceding principles, two ob-. servations can be made:

(a) The electrode forming the control gridi must be placed in a part ofthe cavity resonator where the electric field of the waves is veryslightin such manner that to a large extent the method of vibration of thelatter is not changed; and

(b) the said electrode will preferably be a simple ring (grid withsingle mesh) raised to a direct positive voltage with respect to theother parts of the cavity resonator, the action of this rin beingcombined with that of an external magnetic field. This field has afocusing effec on the electron beam.

The invention will be hereinafter described with reference to Figures 1,3, 5, 6 and 7 showing both structurally and diagrammatically embodimentsaccording to the conditions explained above.

Referring to Figure 1, R1 and R2 indicate two hollow metal chambershaving in the example under consideration, a common wall P, bored withan aperture S. These chambers will, for example, be cylindrical boxes(straight, circular cylinders) the axis of revolution XX of which isnormal to the circular metallic discs A1 and A2 at the centres thereof,these discs being constituted and treated in order to present a highpower of secondary emission. The discs A1 and A2 form a portion of theends of the boxes R1 and R2 but they are separated from the rest of thecavity resonator by above-mentioned insulating joints of material havinglarge surface relative to its thickness. Through this joint, as a resultof its great capacitance, will fiow the high frequency currentcirculating in the inner surface of the resonator. As regards the directvoltage, this joint will perfectly insulate the disc A1 from the rest ofthe resonator. A1 and A2 are both connected with the negative terminalof the battery V0, while the other parts of the cavity resonator, thepermeable cathodes and the connecting pipe are connected with itspositive terminal.

It will thus be seen that the system illustrated in Figure 1 is theequivalent of that illustrated in Figure 2 provided an inductivecapacity system R'1 and R'z is made to correspond to each of theresonators R1 and R2, and its operation as an electron valve is thesame. In order that the system can operate as an amplifier in the mannerindicated in Figure 1, it is sufiicient for the cavities to vibrate inphase, that is to say, for the potentials Va to be added together inamount, their sign being the same (the difference of high frequencypotential between. A1 and A2 being This means that when a positivecharge appears on the face of the wall P which lies within the cavityresonator containin A1, the opposite face of P lying within the othercavity resonator is negative. This result will be attained by excitingeach cavity suitably, for example by means of loops coupling themagnetic field and such as Bi and B2.

A load circuit may also be introduced in the same way.

Naturally, and this will also be the case for: the examples shown inFigures 3 and 4, it is to be implied that a focussing magnetic field isemployed the lines of force of which are parallel to the axis producedby an externalcoil as-shown in Figure 3.

Figure 3 represents another modification in carrying the invention intoeffect which differs from the preceding one by the fact that the part ofeach cavity resonator which is at the direct potential V with respect tothe others is reduced to that which constitutes or immediately surroundsthe ringserving as a grid and surrounding. the beam. Ba and B4 are loopsfor coupling with the load Q. On the diagram the same referencesindicate the same elements as in the preceding figures of the drawings.The ring is shown held up by a disc connected by capacitive joints tothe sides f1 and f2 of the resonators R1 and R2. The capacitativeconnection is necessary in order that the electric field of the highfrequency oscillations in each cavity does not undergo discontinuity atthe edges of the disc and so that-the ring is raised to a high frequencypot'entia'l. If, furthermore, the latter did not exist, the vibrationor" the cavity resonators might be unfavourably altered and possiblyeven prevented. This is furthermore the reason for the use of. a doublecavity.

It will be noted that with the arrangements illustrated the action ofthe electrodes on the electronsdiffers from that of the ordinary transittime multiplier.

In the latter, it is presumed that the field acting on a. secondaryelectron emitted for example at the surface of the electrode A1...corresponds to the difference of high frequency potential between A1 andA2 and to the direct voltage V0 applied between G and A1, This actioncannot exist in the valves described here where each cavity has its ownoscillating field, the two fields interfering with each other in: theconnectin pipe.

Referring to Figure 4 which corresponds to this case, the movement ofthe electrons is as follows: an electron emitted by A1 is subjected inits vicinity to the combined field determined by Tia/2 and by V11 in thecavity I- (thespace formed between A1 and G) and in the latter itremains subjected to this field alone. When it arrives in III (the spaceformed between G and A2) it is the same. The intermediate space IIcannot be regarded as free from field. A bunching of electrons like thatwhich is used in velocity modulation valves, takes place. In this case,the length e must be determined correspondingly in order that thiseffect may be favourable, that is to say, in order that it may produce aphase difference in the advantageous sense, with a suitabledimensioning; it will then be possible to increase the number of theelectrons arriving in proper phase to be slowed down, which improves theefiiciency of the system.

An. example corresponding to a ring of great thickness c with respect tothe distance d between the plates A1 and A2 is illustrated in Figures 5'and 6.

In the example illustrated in Figure 6, as in the example illustrated inFigure 3, the generated profile: of the cavities of revolutionconstitutin the resonator presents a retracted part.

Figure '7 again illustrates an embodiment. embraced by the presentinvention, the design of which, however, considered from the point ofview of the system of the electrodes controlling the movement of theelectrons, differs still more from the system of the usual electronmultiplier. This system similar to that illustrated in Figurecorresponds with a great thickness e of ring. as compared. with thedistance A1A2, to the case of great penetration of the alternating fielddeveloped in a single cavity coupled galvanically to the plates Ar andA2.

In all the systems suggested, it will be understood that the differenceof potential between the side plates of the resonators employed isproduced by the circulation of currents induced by the groups ofelectrons approaching from the electrodes, the capacitative connectionsare thus provided in order to constitute a veritable shortcircuit fromtheir point of view to the frequency of operation.

In a general way, the principal characteristic of the invention consistsin the association of a resonant cavity or a collection of cavitieswith: a system of two secondary emission electrodes separatedby anaccelerating electrode raised to a continuous current potential, thespace between each emittin electrode and the electrode at the directpotential serving successively as acceleration space and as brakingspace for the electrons dueto a rockin movement.

It will be appreciated that according to the present" invention it isnot thesame electronic mass or cloud which carries out a number of timesconsecutively an oscillating movement, but that there are always otherelectrons which travel over the path between: the one and the otheremitting electrode. The rise in the emission by oscillating or rockingmovement is only possible if the electrons always bombard the oppositeelectrode with a velocity which is sufficient to cause the secondaryemission, which must be obtained by i-nterposing between the twoemitting, electrodes. the resonator of whichv the natural period must beadjusted to the electronic time. of travel. Without such a. system ofcontrol of the field; the valve cannot oscillate and cannot evenfurnish. an appreciable emission current.

The invention is naturally capable of numerous modifications, otherthan. those expressly electrons to oscillate in said enclosure at a veryhigh frequency, said enclosure being evacuated,

said means comprising secondary emission cathodes located at the bottomof said cavities facing the openings of said metallic conduit,insulating seals having surfaces large relative to their thicknessarranged around the periphery between said cathodes and said metallicconduit, electronpermeable electrodes constituting the openings of saidmetallic conduit, means in circuit with and adapted to maintain said twoelectrodes at a fixed positive potential relatively to said cathodes, avery high frequency oscillator coupled to both said cavity resonators, aload impedance shuntingsaid cavity resonators relatively tq saidoscillator, and focussing means comprising magnetic field means with itsaxis parallel to the common axis of said cavity resonators? 2. In anelectronic amplifier, the combination, with two identical, cylindrical,cogaxial cavity resonators having a circular base ,aiid highlyconductingwalls, and which are joined together by a cylindrical metallic conduitco-a'xial therewith so as to form a gas-tight enclosure, of means forcausing electrons to oscillate from :one end to the otherbf saidenclosure at a very; high frequency, said enclosure being evacuated,said means comprising a secondary emission cathode located centrally atthe bottom of each cavity.

an annulus located at each end of said conduit, a source of directcurrent supply having the positive pole thereof connected to saidconduit and the negative pole to both said cathodes, a very highfrequency oscillator coupled to both said cavities symmetricallyrelatively to the center of said conduit, insulating seals havingsurfaces large relative to their thickness separating each said cathodefrom the corresponding one of said annuli, a load impedance shuntingboth said cavity resonators relatively to said oscillator, and focusingmeans comprising a magnetic field means with its axis parallel to thecommon axis of said cavity resonators.

3. The combination claimed in claim 2 wherein said two cavities havea'common frontal wall of relatively very small thickness, the length ofsaid metallic conduit being limited to the thickness of said common walland the electrodes thereof being united in a single electrode.

4. The combination claimed, in claim 2 wherein said two cavities have acommon frontal wall and wherein said conduit, being of a length greaterthan the thickness of said common wall, is positioned symmetricallyabout said wall.

ROBERT WARNECKE.

, REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,139,813 Farnsworth Dec. 13,1938 2,295,396 George Sept, 8, 1942 2,337,214 Tunick h Dec. 21, 19432,409,417 Bull Oct. 15, 1946 2516303 7"???1'71'7':

